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4 Answers
4

I would recommend contracting a good designer, perhaps even the individual who designed for the now defunct web design company. For an icon pack, it shouldn't cost much more to commission the icons versus buying stock icons.

The advantages are that you can perfectly match your existing icons (any good designer should be able to match the style), you can get exactly the icons that you need, you have a contact for future icons you may need, and your icons will be unique to your web app, rather than used in multiple places around the web.

The disadvantages are that you need to find a good designer, cost, and your icons will be unique to your web app, rather than used in multiple places around the web.

Think of designing an icon as a two step process. The first one involves developing the concept, and the second one is the actual implementation.

I recommend that you find a good designer. It shouldn't cost you much if the designer doesn't have to develop the concept for you. You can always give him a pre-existing icon or image that you found on the web and ask him to implement it in a style that matches what you are already using.

Instead of finding a matching pack for what you have, you can find or design a pack that has all the icons you want, and then replace the old icons with ones from this new pack. Current users will need to re-learn them, but it should not be difficult if the only thing changing is the icon style and not the concept/representation.